[NOTE] minor breakages here and there in "next"

I am at day-job today but have noticed a couple more minor
breakages coming from the resolve_ref() clean-up done recently
in "next".  Nothing serious or major, but would be nice to fix.

 - git-show-branch does not use '*' for the column for the
   current branch anymore.

 - "git update-index -g" updates everything, not just things
   already different from HEAD.

The latter I think is probably read_ref() around l.446 in
builtin-update-index.c